The invention concerns a voltage controlled generator for sinusoidal waves operating in the ultra high frequency range tuned through control of the capacity (V.C.O.) of L.C. frequency determining circuit incorporating a reverse biased diode which will hereinafter be referred to as a "varicap".
Tunable resonating circuits comprising a varicap which can be used in oscillators have already been described, for example in connection with receivers operating in the frequency bands allotted to radio broadcasting and to television. By way of example, there is described in French Pat. No. 2 032 335, applied for on the 11th Feb., 1970, by the Company MOTOROLA, a television receiver oscillator having a varicap which is tuned by the same control voltage as the varicap resonating circuits provided in the high frequency stages, so as to permit mixing of the received signal into the intermediate frequency of the receiver. Since a varicap diode is an element exhibiting a non linear current voltage characteristic, its presence in a circuit tuned at the frequency f.sub.o results in the production of harmonics at the frequencies 2f.sub.o, 3f.sub.o, and so on.
There have also been described tunable oscillator arrangements comprising two simultaneously controlled resonating circuits comprising varicap, such as in French Pat. No. 2 003 205, wherein a coupling between the two circuits is utilized to increase the bandwidth of the circuit.
The present invention has for its object to provide means for limiting the harmonic ratio of an UHF oscillator which is electronically tunable by means of a varicap.